This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-344194 filed on Nov. 10, 2000.
1. Field of the Invention
The present invention relates to an automatic optical-axis adjusting device for automatically adjusting directions of optical axes of front lights of a vehicle.
2. Description of Related Art
When the vehicle makes a turn, it is possible to adjust the directions of the optical axes of the front lights with respect to a turning direction or traveling direction of the vehicle to improve visibility of a driver. Various control parameters can be used for controlling the directions of the optical axes of the front lights. For example, in one previously proposed automatic optical-axis adjusting device for automatically adjusting the directions of the optical axes of the front lights, a turning radius of the vehicle is used as the control parameter. To provide a less erroneous turning radius of the vehicle, a computing means first computes a value of the turning radius based on each one of output information of a steering wheel sensor arrangement, output information of a vehicle wheel speed sensor arrangement that includes left and right vehicle wheel speed sensors, and output information of a yaw rate sensor arrangement. Next, the computed value of the turning radius derived from the output information of the steering wheel sensor arrangement, the computed value of the turning radius derived from the output information of the vehicle wheel speed sensor arrangement, and the computed value of the turning radius derived from the output information of the yaw rate sensor arrangement are averaged to obtain the less erroneous turning radius. Then, an optical axis control angle is computed based on this turning radius and is used to adjust the directions of the optical axes of the front lights. In such an instance, it is advantageous to transmit the output information from each sensor arrangement to the computing means through a communication bus line. The use of the communication bus line allows a reduction in the number of signal lines for connecting between the sensor arrangements and the computing means in the vehicle.
However, in the above automatic optical-axis adjusting device, if the output information of any one of the steering wheel sensor arrangement, the vehicle wheel speed sensor arrangement and the yaw rate sensor arrangement includes an erroneous value due to, for example, a failure of that sensor arrangement, the averaged turning radius, and hence the optical axis control angle, becomes erroneous.
Furthermore, if noises are present in the communication bus line, the information from each sensor arrangement may become abnormal, resulting in improper adjustment of the directions of the optical axes of the front lights.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide an automatic optical-axis adjusting device for automatically adjusting a direction of an optical axis of each corresponding front light of a vehicle in a more reliable manner with use of a plurality of sensor arrangements.
To achieve the objective of the present invention, there is provided an automatic optical-axis adjusting device for automatically adjusting a direction of an optical axis of at least one front light of a vehicle. The automatic optical-axis adjusting device includes a control parameter computing means for computing a value of a control parameter, which is used for adjusting the direction of the optical axis of the at least one front light, based on output information of each one of a plurality of sensor arrangements. The automatic optical-axis adjusting device also includes a sensor output judging means for determining whether each value of the control parameter, which is derived from the output information of a corresponding one of the plurality of sensor arrangements, is normal. The sensor output judging means first determines whether a majority of the values fall within a predetermined allowable error range. If the majority of the values fall within the predetermined allowable error range, the sensor output judging means determines the majority of the values as normal and the remaining of the values as abnormal. The automatic optical-axis adjusting device further includes a control angle computing means for computing an optical axis control angle, which is used for adjusting the direction of the optical axis of the at least one front light, based on the output information of at least one sensor arrangement, from which the normal value of the control parameter is derived. The automatic optical-axis adjusting device also includes an optical axis adjusting means for adjusting the direction of the optical axis of the at least one front light based on the optical axis control angle by driving an actuator that turns the optical axis of the at least one front light.